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Subject[PATCH 1/7] mm: introduce PageHuge() for testing huge/gigantic pages
Introduce PageHuge(), which identifies huge/gigantic pages
by their dedicated compound destructor functions.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
include/linux/mm.h | 24 ++++++++++++++++++++++++
mm/hugetlb.c | 2 +-
mm/page_alloc.c | 11 ++++++++++-
3 files changed, 35 insertions(+), 2 deletions(-)

--- linux.orig/mm/page_alloc.c
+++ linux/mm/page_alloc.c
@@ -299,13 +299,22 @@ void prep_compound_page(struct page *pag
}

#ifdef CONFIG_HUGETLBFS
+/*
+ * This (duplicated) destructor function distinguishes gigantic pages from
+ * normal compound pages.
+ */
+void free_gigantic_page(struct page *page)
+{
+ __free_pages_ok(page, compound_order(page));
+}
+
void prep_compound_gigantic_page(struct page *page, unsigned long order)
{
int i;
int nr_pages = 1 << order;
struct page *p = page + 1;

- set_compound_page_dtor(page, free_compound_page);
+ set_compound_page_dtor(page, free_gigantic_page);
set_compound_order(page, order);
__SetPageHead(page);
for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
--- linux.orig/mm/hugetlb.c
+++ linux/mm/hugetlb.c
@@ -550,7 +550,7 @@ struct hstate *size_to_hstate(unsigned l
return NULL;
}

-static void free_huge_page(struct page *page)
+void free_huge_page(struct page *page)
{
/*
* Can't pass hstate in here because it is called from the
--- linux.orig/include/linux/mm.h
+++ linux/include/linux/mm.h
@@ -355,6 +355,30 @@ static inline void set_compound_order(st
page[1].lru.prev = (void *)order;
}

+#ifdef CONFIG_HUGETLBFS
+void free_huge_page(struct page *page);
+void free_gigantic_page(struct page *page);
+
+static inline int PageHuge(struct page *page)
+{
+ compound_page_dtor *dtor;
+
+ if (!PageCompound(page))
+ return 0;
+
+ page = compound_head(page);
+ dtor = get_compound_page_dtor(page);
+
+ return dtor == free_huge_page ||
+ dtor == free_gigantic_page;
+}
+#else
+static inline int PageHuge(struct page *page)
+{
+ return 0;
+}
+#endif
+
/*
* Multiple processes may "see" the same page. E.g. for untouched
* mappings of /dev/null, all processes see the same page full of
--



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